Suppose the number of equipment sales and service contracts that a store sold during the last six (6) months for treadmills and exercise bikes was as follows:
Equipment Sales and Service Contracts Sold
Treadmill Exercise Bike
Total Sold 185 123
Service Contracts 67 55
The store can only sell a service contract on a new piece of equipment. Of the 185 treadmills sold, 67 included a service contract and 118 did not.
Complete the following questions in the space provided below:
1. Construct a 95 percent confidence interval for the difference between the proportions of service contracts sold on treadmills versus exercise bikes.
2. Is there a major difference between the two pieces of equipment? Why or why not?
Suppose that there are two candidates (we’ll call them Jones and Johns) in the upcoming presidential election. Sara notes that she has discussed the presidential election candidates with 15 friends, and 10 said that they are voting for candidate Jones. Sara is therefore convinced that candidate Jones will win the election because Jones gets more than 50% of votes.
Answer the following questions in the space provided below:
1. Based on what you now know about statistical inference, is Sara’s conclusion a logical conclusion? Why or why not?
2. How many friend samples Sara should have in order to draw the conclusion with 95% confidence interval? Why?
3. How would you explain your conclusion to Sara without using any statistical jargon? Why?